Even moderate amounts of resistance exercise may help prevent type 2 diabetes, said the study's corresponding author, Duck-chul Lee. He's an associate professor of kinesiology at Iowa State University.

For the study, Lee's team tracked more than 4,500 adults, aged 20 to 100. The investigators found that moderate muscle mass was associated with a 32 percent reduced risk of type 2 diabetes, regardless of problems such as smoking, drinking, obesity or high blood pressure.

The reduced diabetes risk associated with moderate muscle mass was also independent of heart/lung fitness, the findings showed.

Higher levels of muscle strength did not provide additional protection against diabetes. And Lee said there are no standardized measurements for muscle strength, so it's difficult to recommend the ideal amount of resistance exercise.

"Naturally, people will want to know how often to lift weights or how much muscle mass they need, but it's not that simple," Lee said in a university news release.

"As researchers, we have several ways to measure muscle strength, such as grip strength or bench press. More work is needed to determine the proper dose of resistance exercise, which may vary for different health outcomes and populations," he explained.

Getting started with resistance training doesn't require a gym membership or expensive equipment. You can begin at home by doing body-weight exercises, said lead author Angelique Brellenthin, a postdoctoral researcher in kinesiology at Iowa State.

"We want to encourage small amounts of resistance training and it doesn't need to be complicated," Brellenthin said. "You can get a good resistance workout with squats, planks or lunges. Then, as you build strength, you can consider adding free weights or weight machines."

Thirty million Americans have diabetes, according to the U.S. Centers for Disease Control and Prevention. The overwhelming majority suffer from type 2, which is linked to being overweight and sedentary.